Semiconductor light emitting device

ABSTRACT

Disclosed is a semiconductor light emitting device. The semiconductor light emitting device comprises a first semiconductor layer, a second semiconductor layer, an active layer formed between the first semiconductor layer and the second semiconductor layer, a first reflective electrode on the first semiconductor layer to reflect incident light, and a second reflective electrode on the second semiconductor layer to reflect the incident light.

The Application is a Continuation of co-pending application Ser. No.12/307,198 filed on Dec. 31, 2008, which is the national stageapplication of International Patent Application No. PCT/KR2007/006582filed on Dec. 17, 2007, which claims priority of Application No.10-2006-0133528 filed in the Republic of Korea on Dec. 26, 2006 under 35U.S.C. 119; the entire contents of all are hereby incorporated byreference.

TECHNICAL FIELD

The embodiment relates to a semiconductor light emitting device.

BACKGROUND ART

A semiconductor light emitting device comprises an LED (light emittingdiode), an LD (laser diode) and the like. A semiconductor light emittingdevice is used to convert electrical signals into infrared rays, visiblerays and the like by using the characteristics of a compoundsemiconductor and to exchange the converted signals.

In general, an LED has been widely used for household electricalappliances, remote controllers, electric light boards, indicators, andvarious automation devices, and is largely classified as an IRED(infrared emitting diode) and a VLED (visible light emitting diode).

In general, an LED having a small size is fabricated in the form of asurface mount device so that the LED is directly mounted on a PCB(printed circuit board). Accordingly, an LED lamp used as a displaydevice is also fabricated in the form of a surface mount device. Such asurface mount device can replace an existing simple lighting lamp and isused as a lighting indicator producing various colors, a characterindicator, an image indicator and the like.

As described above, such a semiconductor light emitting device has beenused for various fields, for example, electric lights for daily life,electric lights for outputting rescue signals and the like. Further,demand for a high brightness semiconductor light emitting device hasincreased more and more. Thus, a high-power light emitting device hasbeen actively developed.

DISCLOSURE Technical Problem

The embodiment provides a semiconductor light emitting device capable ofimproving the total light emitting efficiency by preventing lightgenerated from an active layer from being absorbed by electrodes.

Technical Solution

An embodiment provides a semiconductor light emitting device comprising:a first semiconductor layer; a second semiconductor layer; an activelayer formed between the first semiconductor layer and the secondsemiconductor layer; a first reflective electrode on the firstsemiconductor layer to reflect incident light; and a second reflectiveelectrode on the second semiconductor layer to reflect the incidentlight.

An embodiment provides a semiconductor light emitting device comprising:a first semiconductor layer; a second semiconductor layer; an activelayer formed between the first semiconductor layer and the secondsemiconductor layer; a first electrode on the first semiconductor layer;and a second electrode on the second semiconductor layer, wherein atleast one of the first electrode and the second electrode is dividedinto a plurality of electrodes.

Advantageous Effects

According to the embodiment, light generated from an active layer isprevented from being absorbed by electrodes, so that the total lightemitting efficiency can be improved.

DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a first embodiment;

FIG. 2 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a second embodiment;

FIG. 3 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a third embodiment;

FIG. 4 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a fourth embodiment;

FIG. 5 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a fifth embodiment;and

FIG. 6 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a sixth embodiment.

MODE FOR INVENTION

In the description of an embodiment, it will be understood that, when alayer (or film), a region, a pattern, or a structure is referred to asbeing “on” ⊚ or “under” ⊚ another substrate, another layer (or film),another region, another pad, or another pattern, it can be “directly” or“indirectly” on the other substrate, layer (or film), region, pad, orpattern, or one or more intervening layers may also be present.

Hereinafter, embodiments will be described with reference to theaccompanying drawings.

FIG. 1 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a first embodiment.

As shown in FIG. 1, the semiconductor light emitting device 100according to the first embodiment comprises a substrate 110, a bufferlayer 120, a first semiconductor layer for example, an n-typesemiconductor layer 130, an active layer 140, a second semiconductorlayer for example, a p-type semiconductor layer 150, a transparentelectrode 160, a first reflective electrode for example, an n-typereflective electrode 170, and a second reflective electrode for example,a p-type reflective electrode 180.

First, the substrate 110 is formed of one selected from the groupconsisting of Al₂O₃, Si, SiC, GaAs, ZnO, MgO or a compound thereof.

The buffer layer 120 may have a stack structure such as AlInN/GaN,In_(x)Ga_(1-x)N/GaN, Al_(x)In_(y)Ga_(1-x-y)N/In_(x)Ga_(1-x)N/GaN and thelike.

The n-type semiconductor layer 130 and the p-type semiconductor layer150 may comprise nitride semiconductor layers, respectively.

The active layer 140 is formed between the n-type semiconductor layer130 and the p-type semiconductor layer 150. The active layer 140 mayhave a single quantum well structure or a multi-quantum well structure.

The transparent electrode 160 is formed on the p-type semiconductorlayer 150. The transparent electrode 160 comprises materials that havesuperior light transmittance and increase diffusion of electric current.The transparent electrode 160 may be formed of transparent conductiveoxide layer, such as ITO, CTO, SnO₂, ZnO, RuO_(x), TiO_(x), IrO_(x) orGa_(x)O_(y).

The p-type reflective electrode 180 is formed on the transparentelectrode 160, and the n-type reflective electrode 170 is formed on then-type semiconductor layer 130.

The p-type reflective electrode 180 and the n-type reflective electrode170 comprise metal containing reflective material to serve as a bondingpad. The p-type reflective electrode 180 and the n-type reflectiveelectrode 170 comprise reflective material such as Ag or Al to have asingle layer structure or a multi-layer structure.

Further, the transparent electrode 160 and the n-type reflectiveelectrode 170 serve as an ohmic contact layer.

For example, the n-type reflective electrode 170 can be formed with anohmic contact layer by using reflective material such as Al. Further,the n-type reflective electrode 170 can be formed with an ohmic contactlayer by using Ti, Cr and the like. Furthermore, the n-type reflectiveelectrode 170 may have a thickness less than several nm in order toincrease the reflectivity of a reflective layer.

Further, the transparent electrode 160 is located below the p-typereflective electrode 180. The transparent electrode 160 serves as anohmic contact layer. Accordingly, the p-type reflective electrode 180can serve as a reflective layer. In addition, the p-type reflectiveelectrode 180 can be prepared in the form of a bonding pad, in which anohmic contact layer 183 is formed by Ti or Cr having a thickness lessthan several nm and a reflective layer 186 is additionally formed.

According to the semiconductor light emitting device 100 of the firstembodiment as described above, the n-type and p-type reflectiveelectrodes 170 and 180 are provided thereto, so that the light generatedfrom the active layer 140 can be prevented from being absorbed by then-type and p-type reflective electrodes 170 and 180. The light generatedfrom the active layer 140 is reflected from the side or bottom surfacesof the n-type and p-type reflective electrodes 170 and 180 instead ofbeing absorbed by the n-type and p-type reflective electrodes 170 and180.

Accordingly, the semiconductor light emitting device 100 of the firstembodiment can improve the brightness thereof. Further, thesemiconductor light emitting device 100 of the first embodiment can beapplied to a low-power semiconductor light emitting device as well as ahigh-power semiconductor light emitting device.

Meanwhile, the embodiment proposes a scheme for dividing a reflectiveelectrode in order to further improve the brightness of thesemiconductor light emitting device. FIGS. 2 to 5 show an example of thesemiconductor light emitting device comprising divided reflectiveelectrodes.

As shown in FIGS. 2 to 5, when dividing a reflective electrode, eitheran n-type reflective electrode or a p-type reflective electrode can bedivided, or both the n-type reflective electrode and the p-typereflective electrode can also be divided. Further, the divided n-typereflective electrodes are electrically interconnected, and the dividedp-type reflective electrodes are also electrically interconnected. Forexample, the divided n-type reflective electrodes can be patterned onthe same plane and the divided p-type reflective electrodes can also bepatterned on the same plane.

FIG. 2 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a second embodiment.

As shown in FIG. 2, the semiconductor light emitting device 200according to the second embodiment comprises a substrate 210, a bufferlayer 220, an n-type semiconductor layer 230, an active layer 240, ap-type semiconductor layer 250, a transparent electrode 260, p-typereflective electrodes 280 and 285, and n-type reflective electrodes 270,272 and 274.

According to the semiconductor light emitting device 200 of the secondembodiment, two p-type reflective electrodes 280 and 285 and threen-type reflective electrodes 270, 272 and 274 are formed.

The two p-type reflective electrodes 280 and 285 formed through divisionare electrically interconnected. According to one example, the twop-type reflective electrodes 280 and 285 can be patterned on the sameplane in the form of a substantial ‘

’ shape.

Further, the three n-type reflective electrodes 270, 272 and 274 formedthrough division are electrically interconnected. The three n-typereflective electrodes 270, 272 and 274 can be patterned on the sameplane.

The two p-type reflective electrodes 280 and 285 are formed on thetransparent electrode 260, and the three n-type reflective electrodes270, 272 and 274 are formed on the n-type semiconductor layer 230.

As described above, the two p-type reflective electrodes 280 and 285 andthe three n-type reflective electrodes 270, 272 and 274 are formedthrough division, so that various light paths can be ensured even whenan area, in which the reflective electrodes are formed in the secondembodiment, is equal to that in which the reflective electrodes areformed in the first embodiment. Accordingly, the light generated fromthe active layer 240 can be more efficiently emitted to the upwarddirection. As a result, the brightness of the semiconductor lightemitting device comprising the divided reflective electrodes can beincreased more and more.

The second embodiment shows an example in which the electrodes formedthrough division are reflective electrodes. However, the electrodesformed through division may be typical electrodes, other than thereflective electrodes, which are applied to fields related to asemiconductor light emitting device.

FIG. 3 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a third embodiment.

As shown in FIG. 3, the semiconductor light emitting device 300according to the third embodiment comprises a substrate 310, a bufferlayer 320, an n-type semiconductor layer 330, an active layer 340, ap-type semiconductor layer 350, a transparent electrode 360, p-typereflective electrodes 380 and 385, and an n-type reflective electrode370.

According to the semiconductor light emitting device 300 of the thirdembodiment, two p-type reflective electrodes 380 and 385 and one n-typereflective electrode 370 are formed.

The two p-type reflective electrodes 380 and 385 formed through divisionare electrically interconnected. According to one example, the twop-type reflective electrodes 380 and 385 can be patterned on the sameplane in the form of a substantial ‘

’ shape.

The two p-type reflective electrodes 380 and 385 are formed on thetransparent electrode 360, and the one n-type reflective electrode 370is formed on the n-type semiconductor layer 330.

As described above, the two p-type reflective electrodes 380 and 385 areformed through division, so that various light paths can be ensured andthe light generated from the active layer 340 can be more efficientlyemitted to the upward direction. Accordingly, the brightness of thesemiconductor light emitting device comprising the divided reflectiveelectrodes can be increased more and more.

The third embodiment shows an example in which the electrodes formedthrough division are reflective electrodes. However, the electrodesformed through division may be typical electrodes, other than thereflective electrodes, which are applied to fields related to asemiconductor light emitting device.

FIG. 4 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a fourth embodiment.

As shown in FIG. 4, the semiconductor light emitting device 400according to the fourth embodiment comprises a substrate 410, a bufferlayer 420, an n-type semiconductor layer 430, an active layer 440, ap-type semiconductor layer 450, a transparent electrode 460, p-typereflective electrodes 480 and 485, and n-type reflective electrodes 470and 475.

According to the semiconductor light emitting device 400 of the fourthembodiment, two p-type reflective electrodes 480 and 485 and two n-typereflective electrodes 470 and 475 are formed.

The two p-type reflective electrodes 480 and 485 formed through divisionare electrically interconnected. According to one example, the twop-type reflective electrodes 480 and 485 can be patterned on the sameplane in the form of a substantial ‘

’ shape.

The two n-type reflective electrodes 470 and 475 formed through divisionare electrically interconnected. The two n-type reflective electrodes470 and 475 can be patterned on the same plane in the form of asubstantial ‘

’ shape.

The two p-type reflective electrodes 480 and 485 are formed on thetransparent electrode 460, and the two n-type reflective electrodes 470and 475 are formed on the n-type semiconductor layer 430.

As described above, the two p-type reflective electrodes 480 and 485 andthe two n-type reflective electrodes 470 and 475 are formed throughdivision, so that various light paths can be ensured and the lightgenerated from the active layer 440 can be more efficiently emitted tothe upward direction. Accordingly, the brightness of the semiconductorlight emitting device comprising the divided reflective electrodes canbe increased more and more.

The fourth embodiment shows an example in which the electrodes formedthrough division are reflective electrodes. However, the electrodesformed through division may also comprise typical electrodes, other thanthe reflective electrodes, which are applied to fields related to asemiconductor light emitting device.

FIG. 5 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a fifth embodiment.

As shown in FIG. 5, the semiconductor light emitting device 500according to the fifth embodiment comprises a substrate 510, a bufferlayer 520, an n-type semiconductor layer 530, an active layer 540, ap-type semiconductor layer 550, a transparent electrode 560, p-typereflective electrodes 580 and 585, and n-type reflective electrodes 570and 572.

According to the semiconductor light emitting device 500 of the fifthembodiment, two p-type reflective electrodes 580 and 585 and two n-typereflective electrodes 570 and 572 are formed.

The two p-type reflective electrodes 580 and 585 formed through divisionare electrically interconnected. According to one example, the twop-type reflective electrodes 580 and 585 can be patterned on the sameplane in the form of a substantial ‘

’ shape.

The two n-type reflective electrodes 570 and 572 formed through divisionare electrically interconnected. The two n-type reflective electrodes570 and 572 can be patterned on the same plane in the form of asubstantial ‘

’ shape.

The two p-type reflective electrodes 580 and 585 are formed on thetransparent electrode 560, and the two n-type reflective electrodes 570and 572 are adjacently formed on the n-type semiconductor layer 530.

As described above, the two p-type reflective electrodes 580 and 585 andthe two n-type reflective electrodes 570 and 572 are formed throughdivision, so that various light paths can be ensured and the lightgenerated from the active layer 540 can be more efficiently emitted tothe upward direction. Accordingly, the brightness of the semiconductorlight emitting device comprising the divided reflective electrodes canbe increased more and more.

The fifth embodiment shows an example in which the electrodes formedthrough division are reflective electrodes. However, the electrodesformed through division may be typical electrodes, other than thereflective electrodes, which are applied to fields related to asemiconductor light emitting device.

FIG. 6 is a sectional view schematically showing the stack structure ofa semiconductor light emitting device according to a sixth embodiment.

As shown in FIG. 6, the semiconductor light emitting device 600according to the sixth embodiment comprises a substrate 610, a bufferlayer 620, an n-type semiconductor layer 630, an active layer 640, ap-type semiconductor layer 650, a transparent electrode 660, p-typereflective electrodes 680 and 685, and an n-type reflective electrode670.

According to the semiconductor light emitting device 600 of the sixthembodiment, two p-type reflective electrodes 680 and 685 and one n-typereflective electrodes 670 are formed.

The two p-type reflective electrodes 680 and 685 formed through divisionare electrically interconnected. According to one example, the twop-type reflective electrodes 680 and 685 can be patterned on the sameplane in the form of a substantial ‘

’ shape.

The two p-type reflective electrodes 680 and 685 are formed on thetransparent electrode 660, and the n-type reflective electrode 670 isformed on the n-type semiconductor layer 630.

As described above, the two p-type reflective electrodes 680 and 685 andthe n-type reflective electrode 670 are formed so that various lightpaths can be ensured and the light generated from the active layer 640can be more efficiently emitted to the upward direction. Accordingly,the brightness of the semiconductor light emitting device comprising thereflective electrodes can be increased more and more.

The sixth embodiment shows an example in which the electrodes formedthrough division are reflective electrodes. However, the electrodesformed through division may be typical electrodes, other than thereflective electrodes, which are applied to fields related to asemiconductor light emitting device.

According to the embodiments as described above, the number of thereflective electrodes formed through division is two or three. However,the number of the reflective electrodes formed through division can bevaried according to the design thereof.

Further, the embodiments show an example of the P-N junctionsemiconductor light emitting device in which the p-type semiconductorlayer is formed on the n-type semiconductor layer. However, theembodiment can be applied to an N-P-N junction semiconductor lightemitting device in which an n-type semiconductor layer is additionallyformed on the p-type semiconductor layer. The N-P-N junctionsemiconductor light emitting device denotes a semiconductor lightemitting device in which both first and second electrode layers areprovided as n-type semiconductor layers, and a p-type semiconductorlayer is formed between the n-type semiconductor layers. At this time, afirst electrode is formed on the first electrode layer, which is then-type semiconductor layer, while making contact with the firstelectrode layer. A second electrode is formed on the second electrodelayer, which is the n-type semiconductor layer, while making contactwith the second electrode layer.

Any reference in this specification to “one embodiment”, “anembodiment”, “example embodiment”, etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

Industrial Applicability

According to the embodiments as described above, the semiconductor lightemitting device comprises a plurality of divided reflective electrodesas electrodes, so that the light generated from the active layer can betransmitted in the upward direction through gaps between the electrodesor reflected from the electrodes instead of being absorbed by theelectrodes. Consequently, the total light emitting efficiency of thesemiconductor light emitting device can be improved.

The invention claimed is:
 1. A semiconductor light emitting devicecomprising: a substrate; a light emitting structure on the substratecomprising a first semiconductor layer including a first portion, asecond portion and a third portion, an active layer on the first portionof the first semiconductor layer, and a second semiconductor layer onthe active layer; a transparent electrode layer on the secondsemiconductor layer of the light emitting structure; a first electrodeon a second portion of the first semiconductor layer; and a secondelectrode on the transparent electrode layer, wherein the transparentelectrode layer has a single layer having a transparent conductive oxidelayer, wherein the second electrode comprises a metal layer and areflective layer disposed on the metal layer, the metal layer directlycontacting at least a portion of a top surface of the single layer,wherein the second portion and the third portion of the firstsemiconductor layer do not overlap with the active layer in a verticaldirection, wherein the first electrode is not on the third portion ofthe first semiconductor layer, wherein a width of the third portion isnarrower than a width of the second portion, wherein the transparentelectrode layer has a first top surface on which the metal layer isdisposed and a second top surface on which the metal layer is notdisposed such that light from the active layer is emitted toward theoutside through the second top surface of the transparent electrodelayer, wherein the second electrode comprises two or more divided parts,at least portions of the two or more divided parts of the secondelectrode being spaced apart from each other, and wherein at least aportion of the second electrode directly contacts the transparentelectrode layer.
 2. The semiconductor light emitting device according toclaim 1, wherein the transparent electrode layer includes at least oneselected from the group consisting of RuO_(x), TiO_(x), IrO_(x), andGa_(x)O_(y).
 3. The semiconductor light emitting device according toclaim 1, wherein the metal layer includes at least one of Ti or Cr. 4.The semiconductor light emitting device according to claim 1, whereinthe first electrode includes a first layer including Ag or Al and asecond layer including Ti or Cr.
 5. A semiconductor light emittingdevice comprising: a substrate; a light emitting structure on thesubstrate comprising a first semiconductor layer including a firstportion and a second portion, an active layer on the first portion ofthe first semiconductor layer, and a second semiconductor layer on theactive layer; a transparent electrode layer on the second semiconductorlayer of the light emitting structure; a first electrode on a secondportion of the first semiconductor layer; and a second electrodecomprising two or more divided parts, the divided parts of the secondelectrode configured to electrically interconnect to each other, whereinthe transparent electrode layer includes an ITO material, wherein atleast portions of the two or more divided parts of the second electrodeare configured to directly contact the transparent electrode layer, andwherein the divided parts of the second electrode comprise a metal layerand a reflective electrode disposed on the metal layer, the metal layerdirectly contacting at least a portion of a top surface of thetransparent electrode layer, wherein the first electrode includes two ormore divided parts, wherein at least portions of the two or more dividedparts of the first electrode are spaced apart from each other, andwherein at least portions of the two or more divided parts of the secondelectrode are spaced apart from each other.
 6. The semiconductor lightemitting device according to claim 5, wherein the metal layer includesat least one of Ti or Cr.
 7. The semiconductor light emitting deviceaccording to claim 5, wherein the two or more divided parts of the firstelectrode are electrically interconnected to each other.
 8. Thesemiconductor light emitting device according to claim 1, wherein adistance from a side of the light emitting structure to the firstelectrode is greater than a width of the first electrode.
 9. Thesemiconductor light emitting device according to claim 1, wherein thefirst portion of the first semiconductor layer is disposed between thesecond portion and the third portion of the first semiconductor layer.10. The semiconductor light emitting device according to claim 1,wherein the second electrode has a first divided part and a seconddivided part, the first divided part being near an edge of thetransparent electrode layer and the second divided part being nearanother edge of the transparent electrode layer, and wherein a distancebetween the first divided part and the second divided part is greaterthan a distance between one of the first divided part and a side surfaceof the transparent electrode layer.